This invention relates to a tube configuration, and mounting for solid oxide fuel cells between a fuel distribution board, and a separator between the generating chamber and combustion chamber, in a tubular, high temperature, solid oxide fuel cell generator apparatus.
High temperature solid oxide fuel cell configurations and generators are well known, and taught, for example, in U.S. Pat. Nos. 4,374,184 (Somers et al.); 4,395,468 (Isenberg); 4,664,986 (Draper et al.); 4,729,931 (Grimble) and 4,751,152 (Zymboly). In these designs, the fuel cells are held in place, primarily by the separator board between the generating chamber and the combustion chamber in the apparatus. The closed ends of the tubes themselves are flat, or more commonly, rounded off, and usually contain an end plug with a flat or domed interior surface. The open ends of the tubes can be tapered near the separator board as shown in U.S. Pat. No. 4,876,163 (Reichner).
In these designs, the generator apparatus is usually operated with the oxidant inlet of the fuel cell tubes up, and the fuel inlet down, and the fuel cells are disposed perpendicular to the ground or plant floor, so that the cells "hang" suspended perpendicular to their separator board support. In some instances, as shown in FIG. 4 of U.S. Pat. No. 4,876,163 (Reichner), the fuel cell tubes, are also supported at the bottom closed end by an insert between the tube and the fuel distribution board. All the cells are bound together and electrically connected by nickel fiber metal strips on the sides of all the cells, binding each cell to its surrounding cells.
In these designs, there is a chance of cell movement due to possible shrinkage of the fiber metal strips after long term continuous operation at 1000.degree. C. Also, the sealed, flat or rounded end of the tubular cells, which must be thin to allow deposition of exterior air electrode, can leak oxidant through the thin end plug. Generally, these tubular cells comprise a supported or unsupported, air electrode, upon which other components are deposited.
The preferred, unsupported air electrode tube is generally extruded. The nature of the extrusion process produces a tube that is open at both ends and must later be plugged at one end to be useful. Closing one end while the tube is still in the plastic state is difficult and could introduce defects. As a result, end closures are made on dried green tubes by insertion of a damp plug and pressing the plug to the inner surface of the green tube. Since a wet plug is introduced into a dried tube, a poor interfacial bond can result and defects in the form of separation cracks can occur. These defects are a concern, since present cell geometry requires this plugged area to remain in the generator proper. Appropriate cell configuration and mounting is desired to eliminate such potential problems. It is a main object of this invention to provide such a configuration and mounting.